1. Field of the Invention
The present disclosure relates to methods of manufacturing thin film transistor (TFT) substrates, and more particularly relates to methods of manufacturing TFT substrates having gate wires with double-layered structures.
2. Description of the Related Art
A liquid crystal display (LCD) includes a common electrode display panel having a color filter and a thin film transistor (TFT) display panel having a TFT array. The common electrode and TFT display panels are opposite to and face each other, and are attached to each other by a seal line disposed therebetween. A liquid crystal layer is formed in a predetermined gap created between the two panels. As described above, an LCD generally includes two substrates, each having an electrode formed on an inner surface thereof, and a liquid crystal layer interposed between the two substrates. In an LCD, a voltage is applied to the electrode to rearrange liquid crystal molecules and control an amount of light transmitted through the liquid crystal layer. Since an LCD is a non-emissive device, a backlight module is required for supplying a source light for a TFT of the LCD. Transmittance of the source light supplied from the backlight module is controlled according to the aligned states of liquid crystals.
In general, a gate wire and a data wire including source/drain are formed on the TFT substrate for use in the LCD. Here, the gate and data wires each may be a single layer, or they may have a double-layered or a triple-layered structure such as to prevent the gate and data wires from being over-etched in a subsequent etching process. For example, the gate wire generally may have a double-layered structure made of a chromium (Cr) layer and an aluminum (Al) layer.
A process of forming the gate wire will now be described briefly. First, chromium and aluminum are sequentially deposited on a glass substrate to form a double-layered stack on the glass substrate, followed by performing exposing and developing the formed double-layered stack using a photo mask to form a pattern. Then, wet etching is performed for sequentially etching the upper aluminum (Al) layer and the lower chromium (Cr) layer, giving a wire corresponding to the mask pattern.
When the upper aluminum (Al) layer and the lower chromium (Cr) layer are wet etched using the mask during formation of the gate wire, a skew phenomenon may occur, so that a width of a chromium gate wire is reduced compared to a width of an aluminum gate wire. The skew phenomenon may be caused by an undercut problem. Defects in an LCD, such as horizontal stripes, result from the undercut problem occurring at the lower chromium (Cr) layer.
One conventional way to avoid such defects is to perform a photo-etch process on each layer independently, or to sequentially etch an upper aluminum (Al) layer and a lower chromium (Cr) layer, followed by etching the upper aluminum (Al) layer once more. In the former case, however, the number of masks used in the process increases, which increases the manufacturing cost. In the latter case, that is, when the upper aluminum (Al) layer is etched twice, adhesion between an upper photo resist (PR) and the upper aluminum (Al) layer is poor, so that a gate wire having a uniform pattern cannot be attained.